Many types of apparatuses have been developed for controlling motion over a distance. For example, many types of linkages have been used for transferring motion, force, or both, over a distance. Such linkages have been used, for example, to operate an actuator that is some distance away. In various applications, a tensile member, such as a rod has been used to transfer the motion or force over a distance. A structural member has been used in opposition to the tensile member, for example, to maintain distance between a local master actuator that is used to produce the force or motion and a more-distant slave actuator that uses the force or motion to accomplish a task. In addition, hydraulic actuators have been used to control motion, and the flow of hydraulic fluid has been controlled to control hydraulic actuators. In some applications, air has been used as a hydraulic fluid.
In a number of applications, it has been necessary or desirable for the distance between the master actuator and the more-distant slave actuator to change, and yet for the linkage to still accomplish its function. Extendable linkage mechanisms have been developed with this capability. Hydraulic systems have also been used wherein the distance between a hydraulic actuator and a hydraulic control device have been varied.
In a specific application, for example, a number of apparatuses or tools have been invented and used for dispensing drywall joint compound, for instance, between sheets of drywall. A number of such drywall tools have handles, and some such handles have linkages associated with, or inside, the handles. Some such handles have been developed that are extendable. But problems have been encountered with such handles, and opportunity for improvement exists.
Drywall, also known as gypsum board, wallboard, and plasterboard, is a building material used to finish the interior surfaces of walls and ceilings in houses and other buildings. Rigid sheets or panels of drywall are formed from gypsum plaster, the semi-hydrous form of calcium sulphate (CaSO4.½H2O), which is typically sandwiched between two layers of heavy paper or fiberglass mats. Drywall sheets are about ½ inch thick and are nailed or screwed in place to form the interior surfaces of the building, and provide fire resistance and sound deadening, among other benefits.
The joints between drywall sheets are typically filled and sealed with strips of paper or fiberglass mat and drywall joint compound, also called “joint compound”, “drywall mud”, or just “mud”. Joint compound may be made, for example, of water, limestone, expanded perlite, ethylene-vinyl acetate polymer and attapulgite. Joint compound may be applied as a viscous fluid that is thick enough to maintain its shape while it hardens. In addition to forming joints, drywall mud is used to cover nail or screw heads, form a smooth or flat surface, and provide a texture over the surface. Paint or wall paper is typically applied over the drywall and joint compound.
Workers often specialize in the installation of drywall, and in large projects, different crews install the drywall panels (drywall hangers) from those who finish the joints and apply the joint compound (tapers or mud men). Workers who specialize in drywall installation often use specialized tools to increase their productivity including flat boxes that are tools used to hold joint compound and apply it to drywall joints. Joint compound is often mixed (e.g., with water) or stored in buckets, and drywall mud pumps have been used to pump the mud from the buckets into flat boxes or other tools or containers.
U.S. Pat. No. 7,473,085, patent application Ser. No. 11/453,455, publication 2007/0292196 (by Werner Schlecht) describes a drywall finishing tool that is commonly referred to as a “flat box”, which is used to apply drywall joint compound between sheets of drywall that are in the same plane (e.g., that form parts of the same wall). Flat boxes have been used successfully for this purpose, and various tools been adapted to apply drywall joint compound to inside corners (e.g., the corners of a room) where sheets of drywall come together, typically, at a substantially right angle.
Examples of tool handles are described in U.S. Pat. Nos. 5,088,147, 5,099,539, 5,182,965, 6,260,238, and 6,412,138, as examples. In a number of embodiments, a master actuator, such as a lever, on a proximal end of the handle is used to operate a slave actuator on a distal end of the handle. The tool (e.g., a flat box) may be attached to a tool head at the distal end of the handle, and, in some embodiments, the slave actuator may be a clamp that may prevent the tool head from rotating about a pivot point at the proximal end of the handle. For example, in the case of a drywall flat box, the worker may position the flat box at the desired angle relative to the drywall surface by pressing the flat box against the drywall surface while holding the handle. The worker may then press the lever, clamping the flat box in the desired orientation. Then the worker may move the flat box along the drywall surface dispensing drywall joint compound in the process, with the flat box clamped into the desired orientation until the clamping action is no longer desired.
Extendable handles for such tools may be extended to the desired length (from a range of available length) before use in a particular situation, and then the length may be fixed using a locking mechanism. The length selected may depend, for example, on the size or height of the worker using the tool, the height of the wall or ceiling to which the drywall joint compound is being applied, or other factors. The patents listed above describe certain extendable linkage mechanisms that provide for adjustments to handle length while maintaining desired operation between the master actuator and the slave actuator.
Needs and potential for benefit exist for adaptations and improvements to certain extendable linkage mechanisms that may be used, for example, for handles for tools, such as drywall tool, or specifically, for instance, handles for flat boxes that may be used to apply drywall joint compound where sheets of drywall come together. Problems that may be overcome by such adaptations and improvements include increasing the useful life of components, reducing cost of manufacture, increasing effectiveness, reducing weight, and the like. In addition, needs and potential for benefit exist for extendable linkage mechanisms, extendable handles, drywall joint compound dispensing tools, and other apparatuses that are inexpensive to manufacture, reliable, easy to use, that have a long life, that are easy to service and clean, and that are simple in operation so that typical operators can effectively maintain them. Room for improvement exists over the prior art in these and other areas that may be apparent to a person of ordinary skill in the art having studied this document. Other needs and potential for benefit may also be apparent to a person of skill in the art of specialized drywall tools.